In the latter half of the twentieth century, school textbooks globally embraced growing emphases on the experiences and rights of diverse marginalized groups. Textbook discussions of diversity earlier in the century, however, have seldom been studied. We use descriptive statistics and regression to examine diversity foci in 978 textbooks from 93 countries published between 1900 and 2013. Unlike previous research, which emphasizes linear growth in diversity-oriented curricula since World War II, our findings reveal a wavelike pattern. We document an early expansionist wave beginning in the 1920s, which was followed by stagnation and decline midcentury before rising again in recent decades. We situate the early expansion within global activities dedicated to diversity in the interwar years and the midcentury contraction within the aftermath of World War II and the geopolitical climate of the Cold War. We contribute to the literature by illuminating the historical ebb and flow of inclusionary educational orientations.